The proposal is to carry out a program of research aimed at developing models of fertility, nuptiality, and mortality to serve as tools of estimation of demographic quantities from deficient and fragmentary data; to facilitate population projections; and, in general, to provide more reliable description of demographic patterns and trends than is possible on the basis of raw data adjusted by use of presently existing models. The development of refinement of model life tables will progress on three main fronts. First, it will make use of international data on causes of death which were not available when the Coale and Demeny model life tables were prepared. By disaggregating and recombining, using a pattern of weights, the life tables can take on greater biological realism. Second, there will be a refinement of the very early and very late ages, in which health changes have the most immediate impact. Third, greater use will be made of Brass' linear logit transformation of standard sets of survival probabilities. Model nuptiality patterns appear to fit the data so well that there is no intention to develop them further except indirectly in the fertility tables. Model fertility patterns are the most recent of the three types and, as is intended, can be considerably extended. Rather than working on purely empirical grounds, as the earlier proposal indicated, there will be an effort to integrate research on birth intervals in natural fertility populations and micro-level models of fecundability, and then to bring in the role of contraception.